3-PHOSPHOGLYCERATE DEHYDROGENASE-DEFICIENCY - AN INBORN ERROR OF SERINE BIOSYNTHESIS

Serine concentrations were markedly decreased ire the cerebrospinal fl uid of two brothers with congenital microcephaly profound psychomotor retardation, hypertonia, epilepsy, growth retardation, and hypogonadis m. The youngest boy also had congenital bilateral cataract. Magnetic r esonance imaging of the brain showed evidence of dysmyelination, Plasm a serine as well as plasma and cerebrospinal fluid glycine concentrati ons were also decreased but to a lesser extent. Treatment with oral se rine in the youngest patient significantly increased cerebrospinal flu id serine and abolished the convulsions. In fibroblasts of both patien ts, a decreased activity was demonstrated of 3-phosphoglycerate dehydr ogenase, the first step of serine biosynthesis (22% anal 13% of the me an control value). This is an unusual disorder as the great majority o f aminoacidopathies are catabolic defects. It is a severe but potentia lly treatable inborn error of metabolism that has not been previously reported in man.